ARM: add C function to switch to non-secure state

The core specific part of the work is done in the assembly routine
in nonsec_virt.S, introduced with the previous patch, but for the full
glory we need to setup the GIC distributor interface once for the
whole system, which is done in C here.
The routine is placed in arch/arm/cpu/armv7 to allow easy access from
other ARMv7 boards.

We check the availability of the security extensions first.

Since we need a safe way to access the GIC, we use the PERIPHBASE
registers on Cortex-A15 and A7 CPUs and do some sanity checks.
Boards not implementing the CBAR can override this value via a
configuration file variable.

Then we actually do the GIC enablement:
a) enable the GIC distributor, both for non-secure and secure state
   (GICD_CTLR[1:0] = 11b)
b) allow all interrupts to be handled from non-secure state
   (GICD_IGROUPRn = 0xFFFFFFFF)

The core specific GIC setup is then done in the assembly routine.

Signed-off-by: Andre Przywara <andre.przywara@linaro.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/arm/include/asm/armv7.h b/arch/arm/include/asm/armv7.h
index 3dcfc8f..b352d43 100644
--- a/arch/arm/include/asm/armv7.h
+++ b/arch/arm/include/asm/armv7.h
@@ -77,6 +77,9 @@ void v7_outer_cache_flush_range(u32 start, u32 end);
 void v7_outer_cache_inval_range(u32 start, u32 end);
 
 #ifdef CONFIG_ARMV7_NONSEC
+
+int armv7_switch_nonsec(void);
+
 /* defined in assembly file */
 unsigned int _nonsec_init(void);
 #endif /* CONFIG_ARMV7_NONSEC */